The technical problem the invention solves is to design an interface between moving parts, such as parts of a folding bicycle or a storage compartment, that automatically and rigidly locks the parts together and may be selectively unlocked without the use of tools.
Various locking mechanisms have been utilized for selectively securing parts. Two known examples are folding bicycles and for airplane stowage bins. For example, U.S. Pat. No. 4,417,745 describes a folding handlebar assembly included in a folding bicycle. The handlebar assembly includes a horizontal tube that is mounted to a steering column post through a transverse mounting tube. The horizontal tube is coupled at each end to a hinge bar and a handle bar portion is slidably attached to each of the hinge bars. In order to place the handle bar portions in an operative position, the handle bar portions are lifted into position and slid over the hinge bars sot that they abut respective ends of the horizontal tube. Pins are then inserted into apertures that extend through the hinge bars and handle bar portions, which prevent subsequent relative motion between the parts.
The assembly suffers from various disadvantages. First, the assembly is not self-locking because it requires manual insertion of the locking pins by the user. Next, it requires the user store the pins when the bicycle is in a folded configuration. Finally, because the locking pins must be closely matched to the size of the apertures, any changes in the dimensions of the apertures or locking pins, such as by normal wear, will cause the assembly to become less rigid.
Another folding handle bar assembly is provided in U.S. Pat. No. 6,301,749 to Chen. That assembly includes a tube, a seat member that is secured to the tube, a pair of hand grips, a clamping bar and a conventional quick release fastener. The seat member and the bar collectively define a channel that is configured to receive an end of each hand grip. The quick release fastener couples the bar to the seat member and allows the user to selectively clamp the hand grips therebetween.
Similar to the previously described locking mechanism, the folding handle bar assembly described in the Chen patent is not self locking and conventional quick release fasteners are notorious for being used improperly. As a result, it requires the user to properly adjust the fastener to achieve a proper clamping force.
An example of a latch assembly used in an airplane stowage bin is shown in U.S. Pat. No. 4,637,642 to Stoecker. That device includes a pivotally mounted latching arm that is moved by a sliding actuating member both of which are attached to a hinged stowage bin door. The actuating member is spring-loaded so that it is forced to abut a portion latching arm which forces latching arm into a latching position. The latching arm includes a generally hook-shaped end that is configured to hook over a striker that is provided on a stationary portion of the stowage bin. The hook-shaped end includes a contact surface that is generally planar and oriented so that a line extending normal to the surface passes above the axis of rotation of the latch arm.
Although the mechanism is designed to be self-locking, the latching arm is specifically designed so that the hinged bin door and the stationary portion are not drawn together. In fact, the latching arm is specifically configured so that stowage bin door can be pushed toward the stationary portion during unlatching. As a result, the mechanism is designed so that there is play between the bin door and stationary portion.
It is desired to provide a self-locking mechanism that provides a rigid interface between two parts that are configured to rotate relative to each other that does not require user adjustment and will not loosen after a period of usage.